Flavored, soluble protein concentrates from peanuts and process for making

ABSTRACT

A process is provided for making flavored soluble protein concentrates from peanuts by grinding, pressing, and extracting with a flash steaming step interposed between the pressing and the extracting. The product concentrates display high protein water solubility and excellent storage characteristics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention lies in the field of peanut protein concentrates andmethods for making the same.

2. Prior Art

Various efforts have previously been made in the field of this inventionto prepare high protein concentrates from peanuts.

So far as is now known, substantially all of the prior art peanutprotein concentrates are characterized by having a relatively highlydeveloped color (being colored from tan to dark brown typically), bybeing relatively strongly peanut flavored, and by being relatively waterinsoluble.

In the prior art peanut protein concentrate preparation procedures,various heat treating steps are characteristically involved particularlyeither before or after an extraction step. This heat exposure isbelieved to effectuate taste development, color changes, proteindenaturization, and perhaps other changes.

For example, Mitchell U.S. Pat. Nos. 3,689,287; 3,800,056; 3,947,599;and 4,052,516 teach processes involving the conversion of peanuts intoprecooked flakes. Typically, ground peanuts are slurried in water,heated with water, and then drum dried to produce flakes. The flakes canthen be extracted, although problems exist in trying to extract theMitchell flakes because of their tendency to break up into powderymaterials which are difficult to separate and to extract.Characteristically, Mitchell employs relatively long heat exposure timeswhich coagulate and denature the protein of the peanut and which causecolor development and taste development in the final product.

For another example, Pominski et al in U.S. Pat. No. 4,355,051 describea direct extraction process for producing a protein concentrate frompeanuts. The starting peanuts are heated, blanched, re-moisturized,flaked, solvent extracted, filtered, de-solventized, and ground intoflour. The flaking procedure of Pominski et al like the flakingprocedure of Mitchell involves heat exposure.

So far as is known, no one has heretofore prepared a particulate blandstorage stable peanut protein concentrate with high water solubilitycharacteristics. During preparation of such concentrate, temperaturesnot above about 100° F. are characteristically involved.

BRIEF SUMMARY OF THE INVENTION

More particularly, the present invention is directed to a particulate,off white to light tan colored, peanut flavored storage stable proteinconcentrate having a high water soluble protein content. Suchconcentrate is derived from peanuts and comprises on a 100 weightpercent total concentrate basis:

(A) from about 60 to 66 weight percent protein,

(B) from about 23 to 28 weight percent carbohydrate,

(C) from about 3 to 4 weight percent dietary fiber,

(D) from about 0.8 to 3 weight percent fat,

(E) from about 0.75 to 1.5 weight percent natural vitamins and minerals,and

(F) from about 0.5 to 3 percent water (moisture).

Such concentrate is further characterized by being in the form of solidparticles at least 90 weight percent of which pass through a 50 meshUSDA standard sieve. Also, such concentrate is characterized by having asolubility in water such that at least about 60 weight percent (on a 100weight percent total starting weight basis) of the total protein presenttherein is soluble in distilled water at ambient temperatures (andpreferably at least about 80 weight percent).

Such a concentrate is made by the steps of:

(a) grinding while maintaining a temperature below about 100° F.shelled, skinned peanuts to produce particles having an average sizeranging from about 0.25 to 0.50 inch (about 6.3 to 13 millimeters),

(b) pressing the resulting so ground material while maintaining atemperature below about 100° F. at a pressure sufficient to express fromabout 10 to 22 weight percent of the starting weight of said so groundmaterial as peanut oil,

(c) flash steaming the resulting so pressed material using steampressures ranging from about 80 to 140 psig and steam temperaturesranging from about 450° to 550° F. applied for a time extending fromabout 3 to 20 seconds, and

(d) subjecting the resulting so steamed material to extraction withliquid hexane until not more than about 1 percent by weight of the totalresulting extracted residue is comprised of peanut oil.

The invention is also directed to processes for producing suchconcentrates.

Various optional steps and conditions are hereinbelow described.

A principal object of the present invention is to provide a particulatestorage stable peanut protein concentrate which is substantially freefrom fat (peanut oil).

Another principal object of the present invention is to provide, in aparticulate storage stable peanut protein concentrate of the typeindicated, a peanut flavored product which has a light color.

Another principal object is to provide, in a peanut protein concentrateof the type indicated, a product having substantial solubility in water.A product having high solubility in water is believed to be desirablenot only from the standpoint of utilization of the concentrate in thepreparation (including cooking) of foodstuffs incorporating such proteinconcentrate, but also from the standpoint of indicating that the proteinmaterial present in such concentrate is in a highly natural state andhas not been significantly denatured or otherwise altered in thepreparation of the concentrate.

Another object of the present invention is to provide process technologywhich will permit production in a simple direct and reliable manner of aprotein concentrate derived from peanuts having product characteristicsas generally above indicated, particularly as regards water solubilitycharacteristics.

Another object is to provide, in a process for preparing a flavoredpeanut protein concentrate from peanuts, techniques for varying flavordevelopment in the product concentrate while effectuating minimumchanges in such concentrates water solubility and color characteristics.

Other and further objects, aims, purposes, features, advantages,embodiments, and the like will be apparent to those skilled in the artfrom the teachings of the present specification taken together with theclaims.

DETAILED DESCRIPTION

The peanuts employed as starting material in the practice of the presentinvention are shelled and preferably skinned initially. If desired, thepeanuts can be pre-dried to a specified moisture content, such as amoisture content below about 40 weight percent (based upon totalstarting shelled and skinned peanut weight). Also, if desired, thehearts can be removed. While it is preferred that the starting peanutshave substantially no exposure to temperatures over about 100° F. inorder to minimize structural changes therein, such as proteindenaturization, it is possible to heat the starting peanuts at atemperature of from about 200° to 250° C. for a time sufficient toeliminate what is generally characterized as the raw peanut taste.Typical times for such a preliminary heating step commonly range fromabout 0.5 to 2.0 minutes.

If desired, the starting peanuts may be blanched. Suitable blanchingconditions comprise raising the temperature to at least 200° F. of thesubstrate with moist heat to inact enzyme activity.

Any convenient grinding procedure can be employed. Coarse grindingprocedures are preferred. Preferably, the average particle size of theground peanuts ranges from about 0.25 to 0.5 inches (about 6.3 to 13millimeters). Smaller and larger particle sizes can be employed, ifdesired, without departing from the spirit and scope of the presentinvention. However, it is presently preferred to avoid particle sizesbelow about 0.1 inch (about 2.5 mm) because particles smaller than thisminimum size can be difficult to retain upon the supporting screensutilized during extraction. Particle sizes greater than about 0.8 inch(about 20 mm ) can be troublesome to extract as desired herein. Grindingis preferably carried out at a temperature below about 100° F. andpreferably below about 90° F.

The resulting so ground peanuts are next subjected to pressing.Preferably, the pressures employed during pressing are sufficient toexpress oil from the ground peanuts to an extent at least sufficient toreduce the starting weight of the ground peanuts by at least about 20percent, and preferably by at least about 23 weight percent. As thoseskilled in the art will appreciate, considerably less oil can be removedby pressing, but then more oil must be removed during the subsequentextraction step. Conventional pressing equipment can be employed.Typical pressing pressures range from about 25 to 200 pounds per squareinch. Pressing is preferably carried out at temperatures below about100° F. and more preferably at temperatures below about 90° F.

Pressing can be accomplished by conventional extractor machines of thetype designed for the expression of oil from seeds, such as cotton seed,flax seed, and the like, as well as for extracting the juice fromfruits. An extraction machine has typically a tapering screw rotating ina cylindrical barrel. Oil removed is delivered to a container while theresidual solids mass is extruded separately. Machines of this type aresometimes also called expellers or expressing equipment. Suitableexpressing equipment is shown and described, for example, in "ChemicalEngineers'Handbook", Fifth Edition, Perry and Chilton, McGraw-Hill BookCompany, Copyright 1973 at pages 19-101 through 19-104.

Optionally but preferably after the pressing, the resulting press cakeis broken up by agitation or the like so as to increase the surface areacharacteristics of the individual particles comprising such. Anyconvenient means for press cake break up can be employed as thoseskilled in the art will appreciate.

After the pressing, and preferably after the press cake has been brokenup, the resulting peanut press cake fragments are subjected to steamflashing (or blasting) using the conditions above summarized.Conveniently the peanut press cake fragments are dispersed or spreadover a screen or mesh, preferably formed of a material such as stainlesssteel, ceramic or glass, and the steam is caused to pop upwardly throughthe mesh and around such fragments.

This steam treatment surprisingly substantially inactivates the enzymespresent in the fragmented peanut material while simultaneously producingonly minimum structural changes in the general chemical structuresthereof. Thus, the peanut oil is substantially unchanged and only aminimum amount of protein denaturization takes place which is believedto be substantially less than the protein denaturization whichinherently takes place when such peanut fragments are subjected to thesubstantially prolonged heat exposures at the lower temperaturespreviously used in the prior art; see, for example, the above referencedteachings of the Mitchell U.S. patents involving pasteurization of anaqueous slurry of peanut particles in water.

This steam treatment produces some slight color changes in the peanutmaterial. Also, concurrently, this steam treatment produces flavordevelopment in the peanut material (which is a desirable peanut flavor).Evidently, the steam treatment induces the occurrence of the Mallardreaction (non-enzymatic browning) which is a reaction between theprotein, the carbohydrates and the water present.

It is theorized (and there is no intent to be bound by theory herein)that in this steam heating treatment, a small amount of the protein isdegraded into peptides and amino acids which react with the carbohydratematerial present. The water present allows the reaction to start. Thesteam pressure and temperature promotes the protein degradation neededto produce the peptides and amino acids required for reaction with thecarbohydrates.

Suprisingly, by regulating the conditions of the steam treatmentprovided by this invention, the color changes and the flavor developmentcan be regulated. Shorter exposure times and lower steam pressures andtemperatures produce smaller color development and flavor development,and vice versa. Steam exposure times, temperatures, and pressures abovethose herein indicated tend to produce such an amount of degradation asto result in dark colored, very strongly flavored treated materialwherein the protein present has been denatured to such an extent thatonly very small amounts thereof are water soluble, all of which isconsidered to be undesirable. The steam treatment conditions taughtherein permit maximum desirable flavor development with minimum colordevelopment and with minimum protein denaturization. By operation withinthe steam treating conditions taught herein the color and flavordevelopment desired for a particular product protein concentrate can beregulated within system limits. Since color and taste are fundamentallymatters of preference and esthetics, no detailed instructions can beprovided herein which will quantitatively produce a specific effect thatwill be optimum for all consumers. While the practice of the presentinvention is suitable for all the basic varieties of peanuts, includingVirginia, Spanish, Runner, and Florunner, those skilled in the art willappreciate that inherent flavor and color variations are associated withindividual varieties which further compounds the difficulties ofspecifying steam treating conditions which will produce a particular enduser desired taste and color combination.

The resulting pressed material is then subjected to extraction with anorganic liquid which is a solvent for peanut oil and which has a boilingpoint below about 125° F. While, as those skilled in the art appreciate,various extraction liquids can be employed, such as, for examples,heptane, isopropyl alcohol, methylene dichloride, acetone, furfural,xylene, liquid sulfur dioxide, and others, at the present time, hexaneis the most preferred material for extraction because of the fact thatsubstantially all of the hexane can be removed following extraction withvirtually no residuals remaining.

Solvent extraction typically in the practice of the present inventioninvolves a mixture composed of the peanut fragments and a liquid. Oilparticularly is removed from the solids (extracted) by exposing themixture of solid and liquid to the action of the solvent. Extraction canbe performed by percolation of the solvent through the solids.

The removal of a soluble fraction, such as peanut oil, in the form of asolution, from an insoluble, permeable solid phase (such as the crushedor ground peanuts), is sometimes termed leaching. The separation usuallyinvolves selective dissolution with or without diffusion. The peanut oilis incorporated within, adsorbed upon, or held mechanically in the porestructure of the insoluble material constituting the peanut fragments.The leaching equipment employed in the practice of the process of thepresent invention may be divided into two principle classes: (1) that inwhich the leaching is accomplished by percolation, and (2) that in whichparticulate solids are dispersed into a liquid and subsequentlyseparated from it. Each includes batch and continuous units. A fewdesigns of continuous machines fall in neither of these major classes.Suitable leaching equipment is described on pages 19-41 through 19-43 of"Perry's Handbook" (reference above cited).

As those skilled in the art appreciate, two steps are always involved insolid-liquid extraction: (1) contact of solid and solvent to effecttransfer of solute to solvent and (2) separation of resulting solutionfrom the residual solid. Various operating methods employed in leachingare disclosed on pages 17-3 through 17.8 of the same above cited"Perry's Handbook".

A present preference is to conduct the leaching operation using acounter current flow of solute to solids at ambient temperatures.

Extraction (leaching) is continued until not more than about 1 percentby weight (based upon the total resulting extracted residue weight) iscomprised of peanut oil (sometimes herein referred to as fat).

The extraction liquid containing dissolved therein the peanut oil isconventionally processed by distillation (evaporation) to separate thepeanut oil (non-volatile) from the extraction liquid (which isvolatile). The volatilized extraction liquid is conventionally condensedand thereafter is reused for further extraction in the processtechnology of the present invention. Conventional separation andrecovery procedures are involved. Such do not constitute part of thepresent invention.

After extraction is completed, the extracted material is preferablydried after removal from the extractor. Drying can be conventionallyaccomplished, but preferably the extracted residue is not heated to atemperature above about 100° F. during drying.

Optionally, the drying can be carried out in combination with, or as apart of, a flash steaming step wherein the steaming conditions are asabove specified for the flash steaming step.

The extracted residue may be employed as such as a food additive or itcan be subjected to further size reduction so as to produce a flour ormeal therefrom. In general, the extracted residue is in the form ofparticles which are easily crushed and broken up. Conveniently, the sizereduction or light grinding operation is carried out under conditionssuch that the final particulate material is in a size such that at leastabout 90 weight percent thereof passes through a 50 mesh USDA standardsieve.

The product (that is, the resulting extracted residue) has a compositionas above indicated in the "Brief Summary" section.

The extracted residues of the present invention constitute a particulateprotein concentrate which is bland, typically virtually colorless (whiteor an off white), and such concentrates are storage stable for anindefinite period of time.

It is theorized (and there is no intent herein to be bound by theory)that the excellent storage stability characteristics of the presentinvention result because of the circumstance that the particulateprotein concentrate products of the present invention are substantiallycompletely defatted. Thus, although small amounts of enzymes appear tobe retained in the product concentrate, such are not in a position toinduce any chemical action in the associated solids owing to the absenceof oil. Because of the processing temperatures (that is, substantiallyambient temperatures) employed in the practice of the present invention,very little change in the protein structure of the starting peanutoccurs. Thus, very little denaturing of the protein fraction resultsduring processing. As a consequence, the protein concentrate products ofthe present invention have their associated excellent solubilitycharacteristics and controlled flavor and color characteristics.

A present particularly preferred class of particulate flavored, colored,storage stable water soluble protein concentrates of the presentinvention comprises on a 100 weight percent total concentrate basis:

(A) from about 60 to 66 weight percent protein,

(B) from about 23 to 28 weight percent carbohydrate,

(C) from about 3 to 4 weight percent dietary fiber,

(D) from about 0.8 to 3 weight percent fat,

(E) from about 0.75 to 1.5 weight percent natural vitamins and minerals,and

(F) from about 0.5 to 3 percent water (moisture).

Such concentrate is further characterized by being in the form of solidparticles at least 90 weight percent of which pass through a 50 meshUSDA standard sieve. Also, such concentrate is characterized by having asolubility in water such that at least about 80 weight percent (on a 100weight percent total starting weight basis) of a 30 gram sample of suchconcentrate is soluble in a liter of distilled water at ambienttemperatures.

Such a concentrate is made by the steps of:

(a) grinding while maintaining a temperature below about 100° F.shelled, skinned peanuts to produce particles having an average sizeranging from about 0.25 to 0.50 inch, (about 6.3 to 13 millimeters),

(b) pressing the resulting so ground material while maintaining atemperature below about 100° F. at a pressure sufficient to express fromabout 10 to 22 weight percent of the starting weight of said so groundmaterial as peanut oil,

(c) flash steaming the resulting so pressed material using steampressures ranging from about 80 to 140 psig and steam temperaturesranging from about 450° to 550° F. applied for a time extending fromabout 3 to 20 seconds, and

(d) subjecting the resulting so steamed material to extraction withliquid hexane until not more than about 1 percent by weight of the totalresulting extracted residue is comprised of peanut oil.

EMBODIMENTS

As is apparent from the foregoing specification, the invention issusceptible of being embodied with various alterations and modificationswhich may differ particularly from those that have been described in thepreceding specification and description. For this reason, it is to befully understood that all of the foregoing is intended to be merelyillustrative and is not to be construed or interpreted as beingrestrictive or otherwise limiting of the present invention, excepting asit is set forth and defined in the hereto-appended claims.

EXAMPLE 1

Raw peanuts are shelled and skinned and then subjected to grinding toproduce particles ranging in size from about 0.25 to 0.4 inch in averagemaximum size.

These particles are pressed at ambient temperature is a screw press andabout 20 weight percent of the starting weight of said particles isremoved and separated as peanut oil.

The press cake resulting is broken up and deposited as a thin layer upona stainless steel fine mesh screen, and steam at a pressure of about 100psig and at a temperature of about 500° F. is passed upwardly throughsuch screen in an autoclave for about 10 seconds.

Therafter, the resulting particles are subjected to counter currentextraction with liquid hexane until the solid residue contains not morethan about 1 percent by weight based on total residue weight of peanutoil.

The resulting residue is then dried at 100° F. until substantially allof the hexane is removed and then the residue is ground at ambienttemperatures to produce a powder at least 90 weight percent which has aparticle size sufficient to pass through a 50 mesh USDA standard sieve.

The powder is bland, substantially white in color, storage stable, andsubstantially free from raw peanut taste. About 85 weight percent of theprotein present in this product powder is soluble in water. Thecomposition of this product is believed to be within the ranges of theparticularly preferred class of concentrates above described.

EXAMPLE 2

The procedure of Example 1 is repeated except that the starting peanutsafter skinning are blanched at 150°-160° C. for 2-3 minutes beforegrinding.

The powdered extracted and dried product appears to have slightly lesspeanut taste and about the same protein solubility.

I claim:
 1. A process for preparing a peanut protein concentratecomprising the steps of:(a) grinding while maintaining a temperaturebelow about 100° F. shelled, skinned peanuts to produce particles havingan average size ranging from about 0.25 to 0.50 inch, (b) pressing theresulting so ground material while maintaing a temperature below about100° F. at a pressure sufficient to express from about 48 to 23 weightpercent of the starting weight of said so ground material as peanut oil,(c) flash steaming the resulting so pressed material using steampressures ranging from about 80 to 140 psig and steam temperaturesranging from about 450° to 550° F. applied for a time extending fromabout 3 to 20 seconds,and (d) subjecting the resulting so pressedmaterial to extraction with liquid hexane until not more than about 1percent by weight of the total resulting extracted residue is comprisedof peanut oil.
 2. The process of claim 1 wherein said resultingextracted residue is dried at a temperature below about 100° F. toseparate residual hexane therefrom.
 3. The process of claim 1 whereinsaid resulting extracted residue is subjected to sufficient grindingaction to reduce the particle size thereof to such an extent that atleast about 90 weight percent thereof passes through a 50 mesh USDAstandard sieve.
 4. The process of claim 1 wherein prior to saidgrinding, said peanuts are exposed to temperatures ranging from about200° to 250° F. for a time sufficient to eliminate the raw peanut taste.5. The process of claim 1 wherein prior to said ginding said peanuts areblanched.